In the retreading art it is known to bond a pre-cured rubber tread strip to a tire periphery with a rubber-based bonding medium which vulcanizes when heat and pressure are applied to the assembly of tire and tread strip. It is also known, as disclosed in U.S. Pat. No. 3,884,739, to retread a plurality of enveloped tires by stacking them vertically on a base with sealing elements disposed between the tires, placing the assembly of stacked tires in an autoclave and effecting seals betwen the enevelopes and their respective tire shoulders by inflating the tires so as to compress the stack between the base and an upper wall of the autoclave.